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Weird Rough Surface on Overhang  

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davep
(@davep)
Trusted Member
Weird Rough Surface on Overhang

I am trying to print this hollow container standing upright on the bed:

This is a side shot. As you can see on either side of the bottom (image is upside down), there is about a 40 degree overhang.

One side of the bottom (left) is nice and smooth - the other side (right) is rough. I am not using supports as I'd like a nice clean finish.

Any ideas why one overhang prints so nice and the other so poorly?

Posted : 25/06/2019 4:42 am
Dave Avery
(@dave-avery)
Honorable Member
RE: Weird Rough Surface on Overhang

whats the orientation on the bed? it likely is the difference in part cooling fan airflow

Posted : 25/06/2019 4:52 am
davep
(@davep)
Trusted Member
Topic starter answered:
RE: Weird Rough Surface on Overhang

Interesting idea - it was horizontal as you face the machine. I'll rotate the model 90 degrees (essentially making it vertical) and try it.

I *think* the cooling fan was blowing on the side that turned out nice and smooth...I'll double check.

Posted : 25/06/2019 4:55 am
davep
(@davep)
Trusted Member
Topic starter answered:
RE: Weird Rough Surface on Overhang

Right. So the side facing AWAY from the fan is the rough side.

After rotating the model 90 degrees (so that neither side faces the fan) they BOTH turned out rough and ugly.

Temp is set at 205/70 and normally is fine for this filament.

Any ideas on what I can do next to solve this?

Posted : 25/06/2019 3:09 pm
Schwach liked
vintagepc
(@vintagepc)
Member
RE: Weird Rough Surface on Overhang

There are many slicer settings you can play with - e.g. drop the filament temp as low as you can for the filament; then it has to cool less and has less time to droop. 

If you're on a mk3 then there is easier low-hanging fruit: there are many user created fan shroud designs on Thingiverse (Dreambox RHD comes to mind) that greatly improve airflow on the far side of prints. 

There don't seem to be any real iterations with the R4/3S fan mount design though so you'd have to consider upgrading the extruder design to something like a skelestruder with a very different fan shroud. that can actually hit the plastic from all sides.

Posted : 25/06/2019 4:01 pm
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(@)
Illustrious Member
RE: Weird Rough Surface on Overhang

Are you using the detect bridging perimeters option? 

Posted : 25/06/2019 7:37 pm
davep
(@davep)
Trusted Member
Topic starter answered:
RE: Weird Rough Surface on Overhang
Posted by: Tim

Are you using the detect bridging perimeters option? 

I am not seeing this nor am I finding it via Google. Is this an actual option in Simplify3D or are you thinking of Slicr?

Posted : 25/06/2019 8:50 pm
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(@)
Illustrious Member
RE: Weird Rough Surface on Overhang

Plicer ... and sorry - missed that you are using S3D.  But I'd be really surprised if it doesn't have a similar switch.

This post was modified 5 years ago by --
Posted : 25/06/2019 10:07 pm
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